Antimicrobial coated metal sheet

ABSTRACT

The present invention relates to metallic sheets having an improved antimicrobial property and also related to a method of manufacturing such sheets. More particularly, it relates to the continuous coating on metallic sheets with a resin composition containing antimicrobial additives. The surface of the metallic article is afforded antimicrobial properties by coating a liquid dispersion or solution of fine particles made of an antimicrobial ingredient on the surface of the metallic sheet dispersed in a uniform layer and cured or dried to affix to the metallic surface. The inorganic antibacterial particles are metal component-supporting oxides and zeolite powders. The inorganic antibacterial core particles have at least a primary surface coating of at least one metal or metal compound having antimicrobial properties. Roll coaters apply the coating. The metallic article generally includes sheet articles made of metals, for example, metallic sheets made of stainless steel, conventional steel sheets and aluminum sheets or plate.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. 119 to U.S.provisional application Ser. No. 60/287,615, filed Apr. 30, 2001 andentitled “Antimicrobial Coated Metal Sheet” the disclosure of which ishereby expressly incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to metallic sheets having animproved antimicrobial property and also related to a method ofmanufacturing such sheets. More particularly, it relates to thecontinuous coating on metallic sheets with a resin compositioncontaining antimicrobial additives.

BACKGROUND OF THE INVENTION

[0003] Recently there has been a trend to develop materials possessingan antimicrobial property generally utilizing a metal, e.g., silver,copper, zinc, etc. Metallic articles, especially stainless steel sheets,are known for their hygienic cleanliness. For example, with stainlesssteel, it is known to add antibacterial properties using metallic layersor alloy layers of chromium, titanium, nickel or iron containing silver,copper and/or zinc formed on their surface by sputtering orincorporating silver in the stainless steel and dispersing silverphases. In addition, it has been known for a long time that silver ionsor copper ions or zinc ions have an antibacterial property. For example,a silver ion has widely been used as a disinfectant in the form ofsilver nitrate. However, the use of silver nitrate as a solution isinconvenient for handling and would have limited durability.

[0004] Generally, the incorporation of silver into a metal object orarticle itself has the disadvantage that the metal's characteristics arealtered by the inclusion of the silver as well as the disadvantage ofthe high cost of the metals themselves. Such a metallic sheet or platehaving the antibacterial ingredient deeply imbedded inside the sheet orplate does not exert any effective action upon bacteria attached to thesurface making incorporation throughout the entire article uneconomical.

[0005] Known thermoset resin compositions have been broadly used ascoating materials for various metals such as iron, aluminum, copper, andstainless steel since the compositions afford a coating which issuperior in luster, transparency, hardness, weather resistance, chemicalresistance and other properties. However, the coating, itself would haveno antibacterial action in and of itself and such coatings often haveinsufficient adhesion to metals making it impossible to endure a formingprocess such as bending. As is apparent from the foregoing, an object ofthe present invention is to provide an antibacterial resin compositionfor coating of metals which withstands bending or forming processes andis usable for coated metal sheets.

SUMMARY OF THE INVENTION

[0006] The present invention provides a polymer composition containingoxide or zeolite particles and having an antibacterial property alongwith processes for coating the surface of metal sheets with suchcomposition. Specifically, the present invention provides for a metalsheet coated with a polymer resin containing inorganic particles withantibacterial properties and the process for making such coated sheets.

[0007] The inorganic antibacterial particles are metalcomponent-supporting oxides and zeolite powders that are made from coreparticles selected form the group consisting of oxides of titanium,aluminum, zinc and copper, sulfates of calcium, strontium and barium,zinc sulfide, copper sulfide, zeolites, mica, talc, kaolin, mullite,zirconium phosphate and silica.

[0008] Preferably, the particles are at least one zeolite at least partof which retains at least one metal ion having a bactericidal propertyat the ionic exchange sites of the zeolite particles.

[0009] The inorganic antibacterial core particles have at least aprimary surface coating or constituent, comprising of from about 0.05 toabout 20% by weight based on the core particles, of at least one metalor metal compound having antimicrobial properties selected from thegroup consisting of silver, copper, zinc, mercury, tin, lead, bismuth,cadmium, chromium, cobalt, nickel, and thallium ions or mixturesthereof. Preferably, the coating or constituent is at least one metal ormetal compound having antimicrobial properties selected from the groupconsisting of silver, copper, zinc, and mixtures thereof.

[0010] According to one embodiment of the present invention, there isprovided a metallic sheet having an antibacterial property characterizedin that the sheet is coated with a polymer composed of at least onepolymer in which is dispersed at least one zeolite at least part ofwhich retains at least one metal ion having a bactericidal property atthe ionic exchange sites of the zeolite particles and methods forproducing such metal sheets.

[0011] The process according to the present invention is characterizedby admixing zeolite particles retaining at least one metal ion having abactericidal property with a polymer or a mixture of polymers prior tocoating onto a metallic sheet. Preferably, the zeolite particles retainthe metal ions having bactericidal properties at ionic exchange sites ofthe zeolite in an amount less than the ion exchange saturation capacityof the zeolite.

[0012] The method of the present invention comprises the steps of (a)cleaning the surface by chemical or mechanical means; (b) surfacepreparation or pretreatment of the metal surface by coating with apretreatment layer appropriate to the base metal to gain proper adhesionproperties; (c) coating the surface of the pretreated metal sheet with auniform layer of an oxide, zeolite or phosphate containing resin and (d)subjecting the coated metal article to curing conditions to cure or drythe resin to produce a hardened and adhered coating to the final sheetproduct.

[0013] After curing, the applied coating composition, a metal sheethaving a cured resin coating adhered thereto is formed generally havingantimicrobial properties. Also, the coating that is formed, typically,has improved fingerprint resistance.

[0014] The film coatings can be used to control the growth of harmfulbacteria, mold and mildew. These film coatings may be applied tostainless or carbon steel products for use in a variety of applications.

[0015] On stainless steels, the zeolite refractory compound, when addedto a clear resin coating, masks the appearance of fingerprints andsmudges due to the light scattering influence of the zeolite particlescontained within the coating matrix. The coating also protects thesurface from staining when tested against kitchen spills such asketchup, mustard and pickle juice.

[0016] Generally, a silver-bearing refractory compound is incorporatedinto polyester or epoxy film coatings to control the growth of harmfulbacteria, mold and mildew. These film coatings may be economicallyapplied to stainless or carbon steel products on full size productioncoils by means of roll coating. The antimicrobial properties may lastfor years depending on the intended application. Clear or pigmented filmcoatings can be used.

[0017] Preferably, silver ions are encapsulated within a zeoliterefractory. The zeolite powder is blended into either a polyester orepoxy resin. A thin film coating, about 0.00025″ thick, is applied toeither a carbon or stainless steel sheet. The silver ions have greatmobility and can diffuse to the surface of the steel to inhibit thegrowth of bacteria and mold.

[0018] Silver has long been recognized for its safe antimicrobialproperties. Coated products may be effective against many common foodborne pathogens such as Escherichia coli, Salmonella and Listeriamonocytogenes as well as various types of mold including Aspergillusniger.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a diagrammatic sectional view of a sheet metal accordingto the present invention.

[0020]FIG. 2 shows flow chart of the process for producing metal sheetscoated with a polymer containing an antimicrobial oxide or zeolite.

[0021]FIG. 3 shows a roll coater or apparatus as an example of thecoating apparatus used in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention provides precoated metal sheets such asiron and steel sheets, aluminum sheets, galvanized and aluminized steelsheets, and stainless steel sheets coated with a polymer containinginorganic antibacterial particles before the metal sheets aremechanically worked into complex shapes as by die pressing, bending,embossing, rolling, and drawing. The inorganic antibacterial particlesare metal component-supporting oxides and zeolite powders that are madefrom core particles selected form the group consisting of oxides oftitanium, aluminum, zinc and copper, sulfates of calcium, strontium andbarium, zinc sulfide, copper sulfide, zeolites, mica, talc, kaolin,mullite, zirconium phosphate and silica.

[0023] For convenience herein, the expression “antimicrobial” or“antibiotic” is used generally to include antibacterial, antifungal,antialgal, antiviral, antiprotozoan and other such activity. Theantimicrobial film of the present invention is particularly effective tothe following bacteria, fungi and yeast: Bacillus cereus var mycoides,Escherchia coli, Pseudomonas aeruginosa, Staphylococcus aureus,Streptococcus feacalis, Salmonella gallinarum, Vibrio parahaemdyticus,Candida albicans, Streptococcus mutans, Legionella pneumophila, Fusobacterium, Aspergillus niger, Aureobasidium pullulans, Cheatomiumglobosum, Gliocladium virens, Pencillum funiculosum and Saccharomycescerevisiae.

[0024] The method of the present invention comprises the steps of (a)cleaning the surface by chemical or mechanical means 40; (b) surfacepreparation or pretreatment 50 of the metal surface by coating with apretreatment layer appropriate to the base metal to gain proper adhesionproperties; (c) coating 60 the surface of the pretreated metal sheetwith a uniform layer of a resin containing a metal component-supportingoxide, phosphate or zeolite powder and (d) subjecting the coated metalarticle to conditions 70 to cure or dry the resin to produce a hardenedand adhered coating to the final sheet product.

[0025] The inorganic antibacterial core particles has at least a primarysurface coating or constituent, comprising of from about 0.05 to about20% by weight based on the core particles, of at least one metal ormetal compound having antimicrobial properties selected from the groupconsisting of silver, copper, zinc, mercury, tin, lead, bismuth,cadmium, chromium, cobalt, nickel, and thallium ions or mixturesthereof. Preferably, the coating is at least one metal or metal compoundhaving antimicrobial properties selected from the group consisting ofsilver, copper, zinc, and mixtures thereof.

[0026] A coated sheet metal according to the invention, indicated by thegeneral reference 10, can be seen in FIG. 1. As used herein, the term“sheet”or “strip”refers to a length of flat metal material of any widthformed in continuous strips or cut to specific lengths. Generally, thesheet is a flat rolled metal product with a width to thickness ratiogreater than about 25 and a thickness of less than about 0.250 inches.

[0027] Sheet 10 comprises a substrate consisting of a metal sheet 12made from metal or metal alloys selected from the group consisting ofaluminum, iron, nickel, titanium, molybdenum, magnesium, manganese,copper, silver, lead, tin, chromium, beryllium, tungsten and cobalt, andalloys of two or more thereof. Examples of the alloys are alloy steelssuch as carbon steel, nickel steel, chromium steel, nickel-chromiumsteel, chromium-molybdenum steel, stainless steel, silicon steel andPermalloy; aluminum alloys such as Al—Cl, Al—Mg, Al—Si, Al—Cu—Ni—Mg andAl—Si—Cu—Ni—Mg; copper alloys such as brass, bronze, silicon bronze,silicon brass, nickel silver and nickel bronze; nickel alloys such asnickel manganese (D nickel), nickel-aluminum (Z nickel), andnickel-silicon.

[0028] Further as the aluminum-based metal, there can be used purealuminum; aluminum oxide; and aluminum alloys for casting and expandingsuch as Al—Cu, Al—Si, Al—Mg, Al—Cu—Ni—Mg, Al—Si—Cu—Ni—Mg alloys, hightensile aluminum alloy and corrosion resistant aluminum alloy. Also asthe iron-based metals, there can be used pure iron, iron oxide, carbonsteel, nickel steel, chromium steel, nickel-chromium steel,chromium-molybdenum steel, nickel-chromium-molybdenum steel, stainlesssteel, silicon steel, Permalloy, non-magnetic steel, magnet steel, caststeel, etc. Preferably, the metal sheet is selected from the groupconsisting of stainless steel, carbon steel, iron, aluminum, aluminizedsteel, galvanized steel, aluminum and steel alloys, magnesium, andmagnesium alloys.

[0029] On one or both of its faces, sheet 12 is coated with anantimicrobial film layer 14 comprising an organic polymer 16. Thepolymer 16 has inorganic antimicrobial powders 18 dispersed within thepolymer comprising an oxide or zeolite core 20 with at least a primarysurface coating or constituent of an antimicrobial metal 22.

[0030] The steels that may be employed for the manufacture of the metalsheet 12 are of various types. One type corresponds to ferritic gradestainless steels that contain 17 wt. % of chromium (Cr) with or withoutmolybdenum (Mo) referred to according to the US Standard as AISI409,AISI 430, AISI 434, AISI 439 and AISI 444, and the French Standard asZ3CTNb18. A second type corresponds to austenitic grades that containfrom about 16 to about 18 wt. % of chromium and at least 2 wt. % ofnickel (Ni) with or without molybdenum, referred to according to the USStandard as AISI 304 and AISI 316. Other stainless steels can beemployed, provided that they contain at least 11 wt. % of chromium. Itis possible, for example, to employ a ferritic steel sheet 12containing, on a mass basis, from about 11 to about 20 wt. % of chromiumand from about 0.2 to about 2 wt. % of nickel.

[0031] In coil-coating processes, a continuous strip of sheet metal isuncoiled at the line entrance and recoiled at the exit, having beencoated or otherwise treated. The line speeds can be up to 200 m/min.

[0032] A process that will be described below manufactures the coatedsheet metal 10.

[0033] 1. Surface Cleaning

[0034] A degreasing operation is recommended to guarantee a goodadherence of the coating. In fact, if the surface of the metal sheet isnot degreased, the fatty substances and other surface contaminants thatare not removed are liable to reduce the adherence of the resin coatingand to give rise to a nonhomogeneous deposit comprising areas withoutcoating.

[0035] The metal substrate is desirably free of contaminants, such aspetroleum greases and oils, that may cause the pretreatment and coatingto be insufficiently adhered to the metal substrate. Consequently, it isdesirable, prior to applying the coating composition, to clean the metalsubstrate. Various methods of cleaning are well known in the art. Theparticular cleaning method should be able to adequately remove residualoil or dirt from the surface but should not cause over-etching of themetal surface. Exemplary cleaning methods include solvent cleaning (suchas a chlorinated solvent (e.g., methylene chloride), ketone (e.g.,acetone), alcohol (e.g., methanol), or toluene, emulsion cleaning,alkaline cleaning, acid cleaning, pickling, salt bath descalingultrasonic cleaning, roughening (e.g., abrasive blasting, barrelfinishing, polishing and buffing, chemical etching and electro-etching).

[0036] The degreasing of the sheet metal is generally performed eitherchemically or electrolytically. The surface of the work piece of metalmay alternatively be cleaned by mechanical means (grinding orsandblasting). The main object of the grinding or sandblasting procedureis to remove impurities or oxides on the surface, to prevent impuritiesfrom contaminating the surface alloy layer. In the mean time, thesurface roughness will be increased after this procedure, whichfacilitates the adhesion of coating. Silicon carbonate sandpaper of #180to #600 is suitable for grinding. Silica sand or other mineral sand canbe used in sandblasting. The sheet metal can be degreased chemically bybeing placed in contact with a solution containing halogenated organicsolvents such as methylene chloride, 1,1,1-trichloroethane,perchloroethylene or trichloroethylene.

[0037] The degreasing operation may be performed electrolytically in anelectrolysis bath or electrolyte consisting of an aqueous solutioncontaining alkaline mixtures similar to those just specified or elsecalcium carbonate or potassium hydroxide. The electrolyte may contain analkaline compound in a proportion of from about 0.5 to about 20 wt. %.The temperature of the electrolyte may be between from about 25° andabout 95° C. The sheet metal may be subjected to a current density ofbetween 0.1 and 20 A/dm² for a period longer than about 0.1 seconds.

[0038] The sheet metal can also be degreased chemically by employing asolution based on alkaline mixtures containing one or more agentsselected from the group consisting of caustic soda, soda ash, alkalinesilicates, sodium hydroxide, sodium carbonate, sodium metasilicate,phosphates, alkaline builders, ammonium acid phosphate, ammoniumhydroxide, monoethanol amine, and dimethylamine oxide and optionallycontaining one or more of the agents selected from the group consistingof complexing agents, surfactants, sequestrant, builders, surface-activeagents, defoaming agents, and mixtures thereof. The alkaline degreasingsolutions and alkaline degreasing agents employed for cleaning metalsurfaces are well known in the literature. Exemplary methods will use asolution of potassium or sodium hydroxide at a concentration of fromabout 1 to about 5%. The degreasing solution is applied to the surfaceof the metal sheet by known spray or dip methods. Generally, these areapplied at a temperature of from about 50 to about 200° C., preferablyfrom about 60 to about 80° C.

[0039] Alkaline builders may be generally classified into three types,namely, the strong alkaline type composed mainly of sodium silicate ortrisodium phosphate and/or caustic soda, medium alkaline type composedof one or more than one of the following; disodium phosphate, sodiumpyrophosphate, sodium carbonate, etc., and mild alkaline type composedof disodium phosphate, sodium bicarbonate, sodium tripolyphosphate,sodium sesquicarbonate, etc. Any alkaline builder of the above types maybe employed therefor.

[0040] The temperature of the alkaline solution is generally betweenabout 25° and about 95° C. Preferably, the temperature of the alkalinesolution is greater than about 50° C. More preferably, the temperatureis greater than about 60° C. The sheet metal is generally subjected tothe solution for a period longer than 0.1 second. Preferably, the sheetmetal is subjected to the alkaline solution for a period longer than 1second. More preferably, the sheet metal is subjected to the alkalinesolution for a period longer than 3 seconds.

[0041] The cleaning bath may have any appropriate pH suitable for theprocess conditions and compatible with the equipment. For example, ifthe equipment is mild steel that is prone to corrosion under acidicconditions, the pH of the cleaning bath should not be so low as to causeacid corrosion. The cleaning bath may be mildly acidic if ammonium acidphosphate is selected as the cleaning agent and, more specifically, hasa pH of from about 2.0 to about 7.5, preferably the agent has a pH offrom about 2.0 to about 5.5, more preferably the agent has a pH of fromabout 2.0 to about 3.5. Alternatively, the cleaning bath may be mildlyalkaline if ammonium hydroxide is selected as the cleaning agent and,more specifically, has a pH of from about 7.0 to about 12, preferablythe agent has a pH of from about 7.0 to about 11, more preferably theagent has a pH of from about 8.0 to about 10.0.

[0042] The concentration of the cleaning agent and the surfactant mustbe sufficient to remove substantially all oil and other contaminantsfrom the metal surface, but must not be so high that a significantamount of foaming occurs. Typically, the water rinse step may be avoidedif the cleaning bath is not too concentrated, which is acceptable in theevent that the metal is initially relatively clean.

[0043] The metal surface having been contacted by the cleaning solutionis generally rinsed with water (neutral medium) or other known rinseagent, also by known spray or dip methods. Air-drying or other dryingmeans generally follows rinsing.

[0044] The surface cleaning step may be eliminated or combined with thesurface pre-treatment step in certain circumstances depending upon thecondition of the metal and the type of pre-treatment utilized.

[0045] 2. Surface Pre-Treatment

[0046] The metal sheet is preferably pretreated to enhance the adhesionof the coating composition after curing. The pretreatment may be, forexample, the formation of an interlayer on the metal substrate surfacethat enhances adhesion of the coating composition after curing. Forexample, the interlayer may be a chemical conversion layer (i.e.,coating), such as a silane, phosphate, chromate, epoxy, or oxide coatingor the interlayer may be an adhesive coating. Generally, thepretreatment is by contacting the metal with chromium phosphate,chromium chromate, zinc phosphate, iron phosphate, or an organicepoxy-based composition.

[0047] The interlayer may be any thickness sufficient to enhance theadhesion of the coating composition during application and after curingbut, in general, the interlayer is at most about 100 percent of thethickness of the cured coating of the antimicrobial composition on oneside, preferably the interlayer is at most about 50 percent of thethickness of the cured coating of the antimicrobial composition, andmore preferably the interlayer is at most about 10 percent of thethickness of the cured coating of the antimicrobial composition. Theinterlayer, typically, is between about 0.01 to about 30 microns thick.Preferably thickness of the interlayer is at least about 0.1 microns,more preferably at least about 0.2 microns and most preferably at leastabout 0.5 microns. Preferably the thickness of the interlayer is at mostabout 20 microns, more preferably at most about 15 microns and mostpreferably at most about 10 microns.

[0048] Generally, the metal surface is pretreated with an aqueouscomposition comprising phosphoric acid and a divalent metal ion when themetal substrate is steel, zinc or zinc based alloys or zinc aluminumalloy coated steel, aluminum or aluminum alloy. Any divalent metal ionmay be used as the divalent metal ion for use in the composition.Generally, the metal is selected from the group consisting of divalenttransition metal ions, such as Mn, Co, Fe, Ni, and Zn, and alkalineearth divalent metal ions, such as Mg, Ca, Sr, and Ba. Preferably thedivalent metal ion is other than nickel for environmental reasons.Preferably the metal is selected from the group consisting of Fe and Zn.Most preferably, the metal is Zn. Silicate may be added to precipitateout any titanium ions that can then be removed from the phosphatingcomposition.

[0049] To accelerate the formation of the phosphate layer, oxidants suchas bromate, chlorate, nitrate, nitrite, organic nitro compounds,perborate, persulfate or hydrogen peroxide, m-nitrobenzene sulfonate,nitrophenol or combinations thereof.

[0050] To optimize the layer formation on certain materials, there isfor instance added sulfate, simple or complex fluoride ions,silicofluoride, boron fluoride, citrate, tartrate, hydroxy-carboxylicacids, aminocarboxylic acids, condensed phosphates, or SiO-containingcompounds (e.g., alkali metal metasilicate, alkali metal orthosilicate,and alkali metal disilicate) and mixtures thereof may be added.

[0051] When the metal surface is predominantly galvanized metal and/orsteel, the pretreatment comprises contacting the metal surface with anaqueous composition comprising phosphoric acid and a divalent metal ion,the composition generally having a total phosphate content from about0.01 to about 3 moles/liter, preferably a total phosphate content fromabout 0.02 to about 2 moles/liter, and more preferably a total phosphatecontent from about 0.1 to about 1 moles/liter. The composition alsogenerally having divalent metal ion content of from about 0.001 to about2 moles/liter (based on metal ion content), preferably a metal ioncontent of from about 0.01 to about 1 moles/liter, and more preferably ametal ion content of from about 0.05 to about 0.5 moles/liter.

[0052] In case of an aluminum, aluminum alloy, or aluminized steelsheet, in order to enhance corrosion resistance, surface hardness andadhesive property of the substrate, it is preferable to form an oxidefilm (alumite) on the sheet by pretreatment (anodizing) with causticsoda, oxalic acid, sulfuric acid or chromic acid.

[0053] The quantities of the components in the composition can vary butare preferably chosen to suit the particular metal which is prevalent inthe surface being treated and therefore depends upon whether the metalsurface being treated is mainly steel, galvanized, aluminum or aaluminum/zinc alloy.

[0054] In particular, for use on aluminum surfaces, it is preferablethat the aqueous composition should also include an activator preferablyfluoride ions. Generally fluoride ions will be provided in the form ofhydrogen fluoride. Fluoride is generally present in amounts up to 1.0moles/liter, preferably in amounts up to 0.5 moles/liter, and morepreferably in amounts up to 0.25 moles/liter.

[0055] In particular in the compositions for pretreatment of galvanizedmetals or steel metal surfaces, preferably the composition also includesboric acid. When the prevalent metal surface for coating is galvanized,boric acid is generally present in an amount of at least 0.02,preferably in an amount of at least 0.05, and more preferably in anamount of at least 0.1.

[0056] In particular in the compositions for pretreatment of stainlesssteel metals or stainless steel metal surfaces, preferably the surfacepretreatment is an epoxy or other organic based pretreatment.

[0057] The pretreatment compositions can be prepared by the addition ofthe components in any convenient order. The phosphating is generallyaimed at providing a fast and efficient treatment for a coil coatingmetal conversion process.

[0058] For coil coating, the pretreatment coating is generally appliedby roll coating or reverse roll coating, or by passing the metal sheetthrough a spray or bath of the composition. However, any other standardapplication form can be used such as by spraying or conventionalspray/dip treatment. Preferably, phosphate pretreatments will be by diptreatment and epoxy pretreatments will be by roll coating. The appliedpretreatment should cover any desired area of the metal substrate to becoated by the final antimicrobial polymer.

[0059] The sheet metal is generally subjected to the solution for aperiod longer than 0.1 second. Preferably, the sheet metal is subjectedto the alkaline solution for a period longer than 1 second. Morepreferably, the sheet metal is subjected to the pretreatment solutionfor a period longer than 10 seconds.

[0060] The pretreatment of the metallic sheet is generally followed by arinsing with water or other neutral rinse medium or dilute chromic acidby known spray or dip methods to remove residual pretreatment solution.This stage is optionally used to ensure removal of any pretreatmentresidues or to seal or cure the pretreatment surface with a final rinseagent. Air-drying or other drying means generally follows rinsing.

[0061] The pretreatment is generally dried by heating and this may becarried out by conventional means, for example by passing the coil orcoated article through an oven or exposing to IR radiation. The dryingtemperature is generally between about 25° and about 95° C. Preferablythe temperature reached on drying or curing is at least 50° C. Morepreferably the temperature reached on drying or curing is at least 60°C. Once the coated metal surface has been dried, the antimicrobialcoating can be immediately applied.

[0062] 3. Coating Composition

[0063] The antimicrobial coatings of the present invention are organicpolymer compositions containing antimicrobial metal-supporting oxide orzeolite particles.

[0064] To prepare the coating composition, any sequence of mixing theconstituents sufficient to form the coating composition may be employed.The mixing or emulsification technique employed may be any suitabletechnique, such as those known in the art. Exemplary mixing techniquesinclude ball, bead or sand milling, high shear mixing, sonic mixing,attritor milling and rapid shaking.

[0065] a. Inorganic Antibacterial Particles

[0066] The inorganic antibacterial particles are metalcomponent-supporting oxides and zeolite powders that are core particlesselected form the group consisting of oxides of titanium, aluminum, zincand copper, sulfates of calcium, strontium and barium, zinc sulfide,copper sulfide, zeolites, mica, talc, kaolin, mullite, silica, zirconiumand zirconium phosphate.

[0067] The inorganic antibacterial core particles have at least aprimary surface coating or constituents, comprising of from about 0.05to about 20% by weight based on the core particles, of at least onemetal or metal compound having antimicrobial properties selected fromthe group consisting of silver, copper, zinc, mercury, tin, lead,bismuth, cadmium, chromium, cobalt, nickel, and thallium ions ormixtures thereof. Preferably, the coating is at least one metal or metalcompound having antimicrobial properties selected from the groupconsisting of silver, copper, zinc, or mixtures thereof and mixturesthereof. Preferably, the amount of antimicrobial component on or in thecore particle is at least about 0.1% by weight, more preferably at leastabout 0.2% by weight, and most preferably at least about 0.5% by weight.Preferably, the amount of antimicrobial component on or in the coreparticle is at most about 20% by weight, more preferably at most about15% by weight, and most preferably at most about 10% by weight.

[0068] The inorganic antibacterial metal component-supporting oxides andzeolite may additionally be coated with a secondary, protective layerselected from the group consisting of silica, silicates, silicondioxide, borosilicates, aluminosilicates, alumina, aluminum phosphate,zinc, zinc oxide, zinc silicate, copper, copper oxide, silanes, andmixtures thereof, among others. The secondary protective layer normallycomprises from about 0.1 to about 20% by weight. Preferably, the amountof secondary protective coating layer on the metal-containing particleis at least about 0.5% by weight, more preferably at least about 0.2% byweight, and most preferably at least about 1.0% by weight of the coatedparticle composition. Preferably, the amount of secondary protectivecoating layer on the metal-containing particle is at most about 10% byweight, more preferably at most about 5% by weight, and most preferablyat most about 3% by weight of the coated particle composition.

[0069] It will be appreciated by those skilled in the art that ifrelatively fine core particles are employed when practicing theinvention, then the practitioner should ensure substantially totalsurface coverage of the first coated core material. While the protectivelayer can be quite dense, the protective layer should be sufficientlyporous to permit diffusion of the antimicrobial component through thecoating at an effective rate and function as a barrier that limits, ifnot eliminates, interaction between the antimicrobial component and asurrounding matrix.

[0070] The inorganic antibacterial metal component-supporting oxides andzeolites, with or without a secondary, protective layer, mayadditionally be coated with a dispersion enhancing coating such as asuitable resin or a hydrous metal oxide, e.g., alumina, hydrous alumina,zirconia, mixtures thereof, among others. This coating corresponds toabout 0.1% to at least about 5% by weight and normally about 0.5 toabout 3% by weight based on the core material.

[0071] The amount of a dispersion aid that is present in theantimicrobial composition ranges between about 0.1% and at least about2.0% by weight based upon the antimicrobial powder, with about 0.5% toabout 1% by weight normally being effective.

[0072] It will be appreciated by those skilled in the art that the ratioof the secondary coatings and dispersion aids can vary widely and may bereadily selected by the artisan.

[0073] The process for preparing the inorganic antibacterial metalcomponent-supporting oxide composition of the invention is described ingreater detail in U.S. Pat. No. 5,180,585; the disclosure of which isincorporated herein by reference.

[0074] Preferably, the inorganic antibiotic particle is an antibioticzeolite. The “antibiotic zeolites”used in the invention are those ofwhich ion-exchangeable ions are partially or completely ion-exchangedwith antibiotic ions. Antibacterial metal-supporting zeolite is knownper se and may be prepared by ion-exchanging zeolite with antibacterialmetals. Examples of the antibacterial metals include silver, copper,zinc, mercury, tin, lead, bismuth, cadmium, chromium, cobalt, nickel,and thallium ions or mixtures thereof. Preference is given to silver,copper, zinc, or mixtures thereof. Particularly, silver alone or acombination of silver with copper or zinc is excellent in antibacterialproperties. Methods for preparing antibacterial zeolite are describedin, for example, U.S. Pat. Nos. 4,525,410, 4,741,779, 4,775,585,4,906,466, 4,911,898, 4,911,899, 4,938,955, 4,938,958, 5,503,840,5,180,585, 5,556,699, 5,595,750, 6,071,542, incorporated herein byreference in their entirety.

[0075] Such zeolites have been incorporated in antibiotic resins (asshown in U.S. Pat. Nos. 4,938,955 and 4,906,464) and polymer articles(U.S. Pat. No. 4,775,585) while other uses are described in U.S. Pat.Nos. 5,714,445; 5,697,203; 5,562,872; 5,180,585; 5,714,430; and5,102,401, all incorporated herein by reference in their entirety.

[0076] In the antibiotic film of this invention, either natural orsynthetic zeolites may be used as the “zeolite component”. Zeolites arealuminosilicates, of either natural or synthetic origin, which havesites at which cationic exchange may occur. By treating them withsolutions of metal ions, a desired antimicrobial metal ion can besubstituted in the zeolite structure.

[0077] Zeolite is generally aluminosilicate having a three dimensionallygrown skeleton structure and is generally represented byXM_(2/n)—Al₂O₃—YSiO₂—ZH₂O, written with Al₂O₃ as a basis, wherein Mrepresents an ion-exchangeable metal ion, which is usually the ion of amonovalent or divalent metal; n corresponds to the valence of the metal;X is a coefficient of the metal oxide; Y is a coefficient of silica; andZ is the number of water of crystallization. There are known variouskinds of zeolites having different component ratios, fine porediameters, and specific surface areas. As the zeolite used in thepresent invention, any natural or synthetic zeolites can be used.

[0078] Examples of natural zeolite include analcime, chabazite,clinoptilolite, erionite, faujasite, mordenite, and phillipsite. On theother hand, typical examples of synthetic zeolite include A-typezeolite, X-type zeolite, Y-type zeolite, and mordenite. A syntheticzeolite is preferably used as the zeolite in the present invention. Asalready mentioned above, the antibiotic zeolites as used herein arethose of which ion-exchangeable ions such as sodium ions, potassiumions, calcium ions, magnesium ions and iron ions are partially orcompletely ion-exchanged with the aforementioned antibiotic metal ionssuch as silver, copper or zinc ions or mixtures thereof.

[0079] The shape of zeolite may preferably be powdery particulate. Aparticle size of the zeolite can suitably be selected depending onapplication. For films of the present invention, the average particlesize is generally 10 microns or less, preferably the average particlesize is 6 microns or less, more preferably the average particle size is5 microns or less. For films of the present invention, the averageparticle size is generally 0.1 microns or more, preferably the averageparticle size is 0.2 microns or more, more preferably the averageparticle size is 0.5 microns or more.

[0080] The metal is preferably supported on solid particles of zeolitethrough an ion-exchange reaction. Zeolite is preferably ion-exchangedwith metal ions in an amount of less than an ion-exchangeable amount ofthe zeolite particles, particularly in an amount less than about 100%,preferably in an amount less than about 90%.

[0081] It should be understood that the amount of the metal incorporatedin the metal-zeolite might vary depending upon the metal used andwhether or not combinations of metals are used. In the case of silveralone, the amount of the metal incorporated in the metal-zeolite isgenerally 20% by weight or less, preferably from about 0.001 to about15% by weight, more preferably from about 0.01 to about 10% by weight,most preferably from about 0.05 to about 5% by weight, based onanhydrous zeolite plus metal.

[0082] In the case of zinc or copper, the amount of zinc or copperincorporated in the metal-zeolite is generally 25% by weight or less,preferably from about 0.001 to about 20% by weight, more preferably fromabout 0.01 to about 15% by weight, most preferably from about 0.05 toabout 10% by weight, based on anhydrous zeolite plus metal. It ispossible to use two or more of silver, copper, zinc and the other metalions together. In this case, although the total amount of the metal ionsis dependent on the composition of the metal ions, it is generally 25%by weight or less, preferably from about 0.001 to about 20% by weight,more preferably from about 0.01 to about 15% by weight, most preferablyfrom about 0.05 to about 10% by weight, based on anhydrous zeolite plusmetal.

[0083] It is possible to also incorporate other ions than theantibacterial metal ions, for example, sodium, potassium, magnesium,calcium, aluminum, titanium, cerium and other metal ions. Accordingly,these ions may remain or co-exist.

[0084] After drying, the antibiotic zeolites thus obtained arepulverized and classified and then are incorporated into a desiredresin.

[0085] b. Polymers

[0086] The metal coating compositions are generally based on aminoalkylresins, aminoacrylic resins, epoxy resins, and polyurethane resins. Inthe present invention, the organic polymeric materials used for formingantibiotic-containing films may be any synthetic, natural orsemi-synthetic organic polymers so far as they can be formed into films.Generally, such polymers are thermoplastic polymers or thermosetpolymers. Examples of such organic polymeric materials include, but arenot limited to, acetate rayon, acrylic resins,acrylonitrile-butadiene-styrene (ABS) resins and acrylic resins,aliphatic and aromatic polyamides, aliphatic and aromatic polyesters,allyl resin, (Allyl), AS resins, butadiene resins, chlorinatedpolyethylene, conductive resins, copolymerised polyamides, copolymers ofethylene and vinyl acetate, cuprammonium rayons and natural andsynthetic rubbers, EEA resins, epoxy resins (e.g. bisphenol,dihydroxyphenol, and novolak), ether ketone resins, ethylene vinylalcohol, (ENAL), fluorine resins, fluorocarbon polymers, fluoroplastics,(PTFE), (FEP, PFA, CTFE, ECTFE, ETFE), high density polyethyelenes,ionomer resins, liquid crystal polymer, (LCP), low densitypolyethylenes, melamine formaldehyde, (melamine resins), naturalpolymers such as cellulosics, nylons, phenol-formaldehyde plastic, (PF)phenolic resins, polyacetal, (acetal), polyacrylates, (acrylic),polyacrylonitrile, (PAN), (acrylonitrile), polyamide, (PA), (nylon),polyamide-imide, (PAI), polyaryletherketone, (PAEK), (ketone),polybutadiene, (PBD), polybutylene terephthalate, polybutylene, (PB),polycarbonate, (PC), polycarbonates, polydicyclopentadiene, (PDCP),polyketones, (PK), polyester block copolymers, polyesters,polyesterurethane, polyesterurethaneurea, polyether and polyester blockpolymers, polyether ketoneketone (PEKK), polyetherether ketone (PEEK),polyetherimide, (PEI), polyethers, polyethersulfone, (PES),polyetherurethane, polyetherurethaneurea, polyethylene isophthalate,polyethylene terephthalate, polyethylene, (PE), polyethylenechlorinates,(PEC), polyglycolic acid, polyhexamethylene terephthalate, polyimide,(PI), polylactic acid, polymethylpentene, (PMP), poly-m-phenyleneisophthalamide, polyolefins, polyphenylene oxide, (PPO), polyphenylenesulfide, (PPS), polyphthalamide, (PTA), poly-p-phenyleneterephthalamide, polypropylene, (PP), polysiloxanes such as polydimethylsiloxane, polystyrene, (PS), polysulfides, polysulfone, (PSU),polytetrafluoroethylene, polyurethane, (PU), polyvinyl acetate,polyvinyl alcohols, polyvinylchloride, (PVC), polyvinylidene chloride,(PVDC), polyvinylidene fluoride and polyvinyl fluoride, rayon,reconstituted silk and polysaccharides, reinforced polyethyleneterephthalate resins, segmented polyurethane elastomers, siliconeresins, spandex or elastane elastomers, styrene type specific resins,thermoplastic polyurethane elastomers, thermosetting synthetic polymerssuch as phenol-formaldehyde copolymer, triacetate rayon, unsaturatedpolyester resins, urea resins, urethane resins, vinyl chloride resins,vinyl polymers, and vinylidene chloride resins. This group includesreasonable copolymers, terpolymers and mixtures of the species listed.

[0087] The polymer can be dissolved in suitable solvents or in somecases, dispersed in a suitable liquid or solvent mixture. This mayinclude water. Examples of organic solvents include toluene, xylene,methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butylacetate, cyclohexanone, cyclohexanol, and mixtures thereof. Inaccordance with the invention, any suitable polymer may be selected byone skilled in the art which is capable of functioning as a matrix forthe antimicrobial agents used (and other optional ingredients) andcoating the specified sheet metals. It is evident that depending on theparticular application or use and other pertinent considerations, anappropriate choice of polymer can readily be made.

[0088] The organic polymer acts as a carrier and matrix for the oxidesand zeolites further described herein and also as a protective barriercoating for the sheet metal substrates.

[0089] Admixing the antibiotic zeolite and an organic polymeric compoundin a usual manner and then coating the mixture obtained onto themetallic sheet (forming it into films) can produce the coated productsof the present invention. The formation of the film can be carried outaccording to any known methods for roll coating polymer coatings.

[0090] Solvents (or liquids to disperse the polymer) which are useful inaccordance with the invention include but are not limited to aliphatichydrocarbons, aromatic solvents, alcohols and other oxygenated solvents,substituted hydrocarbons, phenols, substituted aromatic hydrocarbons andhalogenated aliphatic hydrocarbons. Each resin system has a group ofsolvents and diluents compatible with the resin and suitable for filmforming. In some cases the organic solvent is only used to disperse theresin powder. It is contemplated that water can be used assolvent/diluent or dispersant for some resin compositions.

[0091] The polymer coatings according to the present invention maycontain other additives as well as antimicrobial compositions. They maycontain, for example, polymerization catalysts, stabilizers, delusteringagents, optical whitening agents, organic or inorganic pigments,inorganic fillers, plasticisers and so on. It is also possible that theantimicrobial particles themselves can fulfill a dual role and providethe benefits of some of the aforementioned additives.

[0092] To the present antibacterial zeolite may be added white pigmentssuch as magnesium oxide, calcium oxide, aluminum oxide, zinc oxide,titanium dioxide, silicon dioxide, calcium carbonate, magnesiumcarbonate and barium sulfate. In addition, to the present antibacterialoxide or zeolite may be added additives such as magnesium silicate,aluminum silicate, zinc silicate, silica gel-zinc, synthetichydrotalcite, aluminum tripolyphosphate.

[0093] Conventional procedures for incorporating powders in polymercompositions may be used to prepare the polymer articles of theinvention. The antimicrobial powders may be added to a monomer or to anintermediate product prior to polymerization. However, generally theyare mixed or compounded with a finished polymer before it is applied asa film. Precoating of antimicrobial particles with polymer greatlyfacilitates incorporation of the particles in the bulk polymer. This maybe done, for example, by slurrying the antimicrobial powder with asolution of the polymer, then removing the solvent by drying. From about0.1 to about 10% by weight of polymer based on the coated powder andpreferably from about 0.5 to about 5% by weight of polymer based on thecoated powder is suitable for this purpose.

[0094] In another embodiment, the coating is placed onto a metal sheetwherein the coating composition is comprised of dispersed epoxy resinparticles. Preferably, the metal sheet treated with an epoxypretreatment is stainless steel or aluminum. The epoxy resin may be asolid or liquid epoxy resin. Preferably the epoxy resin is a liquid thatis dispersed (i.e., emulsified) within the solvent. Exemplary epoxyresins include diglycidyl ether of bisphenol A, such as those availablefrom The Dow Chemical Company, Midland, Mich. under the trade nameD.E.R., and from Shell Chemical Company, Houston, Tex. under the tradename EPON or EPI-REZ and phenol and cresol epoxy novolacs, such as thoseavailable under the trade name D.E.N. from The Dow Chemical Company,Midland, Mich. Other examples of useful epoxy resins include thosedescribed in U.S. Pat. Nos. 5,118,729, 5,344,856 and 5,602,193, eachincorporated herein by reference. The amount of epoxy resin in thecoating composition may be any amount sufficient to coat a metalsubstrate that, subsequently, can be cured to form a corrosion resistantcoating on the metal.

[0095] The epoxy coating composition may also contain a surfactant thatforms an epoxy resin in water dispersion, wherein the epoxy resinmolecules have a neutral or positive surface charge, the surfactantbeing a nonionic surfactant, amphoteric surfactant or mixture thereof.

[0096] The nonionic surfactant may be, for example, a nonionicsurfactant or combination of surfactants known to form oil in wateremulsions. Exemplary nonionic surfactants include polyglycol ether of anepoxy, an alcohol, fat, oil, a fatty acid, a fatty acid ester or analkylphenol. Exemplary amphoteric surfactants include those known in theart, such as alkyl betaines and dihydroxyethyl glycinates.

[0097] The amount of surfactant present in the coating composition maybe any amount sufficient to disperse the epoxy resin and cause the epoxyresin particles in the dispersion to have a neutral or positive charge.Generally, the amount of surfactant is at least about 0.1 percent byweight, preferably is at least about 0.5 percent by weight. Generally,the amount of surfactant is at most about 10 percent, preferably is atleast about 5 percent by weight of the total coating composition weight.

[0098] The epoxy coating composition optionally also contains a latentcuring agent. Examples of latent curing agents include dicyandiamide andblocked isocyanates, such as an alcohol-blocked toluene diisocyanate.Preferably the latent curing agent is dicyandiamide. The amount oflatent curing agent is an amount sufficient to cure the epoxy resin andgenerally should be an amount that is not so great that the coating,after curing, fails to provide improved corrosion resistance of a metalsubstrate. Generally, the amount of latent curing agent is at leastabout 0.1 percent by weight, preferably is at least about 0.5 percent byweight. Generally, the amount of latent curing agent is at most about 10percent, preferably is at least about 5 percent by weight of the totalcoating composition weight.

[0099] The aqueous epoxy coating composition, of course, contains waterin an amount sufficient, for example, to provide an epoxy in wateremulsion when the epoxy is a liquid. The water should also besufficiently pure to provide a water matrix that fails to causecoagulation of the particles (e.g., epoxy or filler particles) due, forexample, to impurities (e.g., ionic impurities).

[0100] c. Additional Additives

[0101] The polymer film compositions of the present invention may beclear or may contain pigment particles or dyes. The pigment particlesare preferably titanium dioxide, alumina or silica. Preferably, pigmentparticles are titanium dioxide particles are from about 0.1 to about 10microns in median particle size, preferably from about 0.2 to about 5microns in median particle size.

[0102] The coating may further be comprised of fillers that impart, forexample, opacity or improved wear resistance to the coating compositionafter it has been cured. Exemplary fillers include ceramic particles orwhiskers and known surface treated metal pigments.

[0103] Preferably the filler is a ceramic selected from the groupconsisting of oxides, borides, nitrides, carbides, hydroxides,carbonates, silicides, silicates and alloys thereof.

[0104] When the coating composition contains the filler, the filler isgenerally present in an amount of about 1 percent to about 50 percent byweight of the total coating composition weight. Preferably the amount ofthe filler, when present, is at least about 2 percent, more preferablyat least about 5 percent. Preferably the amount of the filler, whenpresent, is at most about 40 percent, more preferably at most about 35percent.

[0105] If desired, the coating composition may also contain across-linking catalyst, for example, to increase the rate ofcross-linking (i.e., cure) of the epoxy at a temperature. Generally, thecatalyst may be, for example, a tertiary amine or imidazole. Examples ofthe catalyst that may be employed in the coating composition include2-methylimidazole, benzyldimethylamine, dimethyl aminomethyl phenol andtris(dimethylaminomethyl)phenol. Preferably the catalyst is2-methylimidazole.

[0106] When the coating composition contains the catalyst, the catalystis generally present in an amount of about 0.001 percent to about 1percent by weight of the total coating composition weight. Preferablythe amount of the catalyst, when present, is at least about 0.002percent, more preferably at least about 0.005 percent and mostpreferably at least about 0.01 percent to preferably at most about 0.7percent, more preferably at most about 0.5 percent and most preferablyat most about 0.3 percent by weight of the total weight of the coatingcomposition.

[0107] If necessary or desired, the coating composition may also containa small amount of defoamer. The defoamer may be any suitable defoamer,such as those known in the art. Exemplary defoamers includesiloxane-based defoamers. The defoamer, when present, is present only ina quantity necessary to control the foaming of the coating composition,since it has been found that, in general, the defoamer impedes theadherence of the coating composition to a metal substrate. The amount ofdefoamer, when present, is generally present in an amount of at mostabout 0.15 percent, more preferably at most about 0.05 percent and mostpreferably at most about 0.02 percent by weight of the total weight ofthe coating composition.

[0108] 4. Coating Application

[0109] The pretreated metal sheet is then coated with an antimicrobialpolymer composition that includes inorganic antimicrobial particlesdispersed in an organic polymer. Exemplary coating polymers are theepoxies, polyvinyl chloride, acrylics, polyurethanes, fluorocarbons, andpolyesters. The suitable epoxies include phenolic-modified epoxies,polyester-modified epoxies, epoxy-modified polyvinyl chloride, epoxymelamines and cross-linkable epoxies.

[0110] A conventional roll coater apparatus 60 as known in the artapplies the coating to the substrate 12. In one embodiment, as depictedin FIG. 3, roll coaters may be used to coat both of the substrate 12surfaces.

[0111] Optionally, only one surface may be coated. Preferably, the rollcoater is a two-roll coater as illustrated in FIG. 3, utilizing apick-up roll 64 that is fed liquid polymer from a paint tray 66 andtransfers the liquid to an applicator roll 62. The applicator roll 62applies and smoothes the liquid onto the substrate 12 surface. Inanother embodiment, the sheet may be coated in more than one applicationto the same sheet in order to provide additional thickness to the finalcoating. Such multiple coatings may have additional washing, drying andcuring stages associated with each coating.

[0112] Optionally, the substrate is heated, at least one surface, at thetime of application and/or subsequently to a temperature equal to orabove the temperature needed to cure the coating and below the substrateoutgassing and/or degradation temperature, so that the coatingsufficiently flows and forms a smooth continuous coating film, and thencures to a thermoset state or dried to a thermoplastic state withoutdegrading the substrate.

[0113] Heating can be performed in infrared, convection ovens, inductionor a combination, although convection ovens are preferred. Time andtemperature of the final cure will vary somewhat depending on thecoatings employed and conditions of use. However, regardless of curetime and temperatures employed, provided that the liquid coatingingredients have been sufficiently flowed onto the substrate beforecuring, the coating films generated on the substrates will have avisually consistent appearance and will be without entrapped bubblesthat interfere with the aesthetic appearance and distinctness of imagerequired by conventional standards.

[0114] Referring to FIG. 2, reference numeral 100 generally refers to acoating line incorporating the invention. A metal strip 12 such asannealed cold reduced steel is passed directly from the manufacturing ofa strip or is unwound from a coil on an uncoiler by drive rollers. Aftersurface treating, the strip 12 is horizontally passed through a rollcoater 60 where liquid polymer is deposited onto the top and/or bottomsurface of strip 12. It will be understood that strip 12 also could bevertically passed through coater 60. After being coated with a liquid,strip 12 is passed through a hardening device 70 (e.g., a convectionoven) wherein the powder is at least partially hardened by drying orcuring. Optionally, after the flowing and/or curing is completed, thecoating may be cooled rapidly to form a tightly adherent coating bypassing the coated strip through an air or liquid quench, such as water(not shown). The quenched strip can then be dried by a dryer (notshown), such as a pair of air knives for blowing the water from strip12. Coated strip 10 then may be cut into lengths by a shear or rewoundinto a coil by a coiler.

[0115] Coating line 100 optionally may include a pair of opposingpresses, a cleaner, or a preheater. After surface pretreatment 50, strip12 may be preheated e.g., by passing through an induction heater.

[0116] Generally, the content of the antimicrobial metal containingparticles in the final coating ranges from about 0.2 to about 30 weightpercent based on the final, dried film weight of the coating. This isalso on a weight percent based on the weight of the total solids of theapplied coating (prior to the evaporation of solvent). The content ofthe antimicrobial particles in the final coating of the presentinvention is preferably at least about 0.5 weight percent, morepreferably at least about 2 weight percent, and most preferably at leastabout 5 weight percent based on the final, dried film weight of thecoating. The content of the antimicrobial particles in the final coatingof the present invention is preferably at most about 25 weight percent,more preferably at most about 20 weight percent, and most preferably atmost about 15 weight percent based on the final, dried film weight ofthe coating.

[0117] When coating a metal substrate with the coating composition ofthe present invention, the coating composition is applied to the metalusing any suitable technique, such as blade coater method, gravurecoater method, beat coater method, roll coater method, curtain flowcoater method, dip coater method, and spray coater method, spin coating,brushing, and electro-deposition. The applied coating should cover thearea of the metal substrate that is desired to be coated.

[0118] In an alternate embodiment, the metal sheet is coated in morethan one application using at least two different types of coatings. Inone exemplary method, the first application is a paint or polymercoating without antimicrobial oxide or zeolite additives. At least thefinal coating application is a polymer coating containing antimicrobialoxide or zeolite additives. The first layer can be used to impart eitheradditional thickness of the total coating, to minimize the total amountof antimicrobial oxide or zeolite additives necessary to coat a givensheet (since only the top surface must have these additives), or toimpart other characteristics as known in the art, e.g., additionalcorrosion resistance coatings, additional or alternative colorants,improved hardness, weather resistance, chemical resistance and otherproperties.

[0119] 5. Coat Curing, Drying or Setting

[0120] After a coating composition is applied, the coating is at leastpartially cured or dried to harden and adhere the coating to the metalsheet. The curing is by means suitable to the polymer composition used.Curing can be by heating, infrared radiation, fluorescent radiation,ultraviolet radiation, gamma or beta radiation, X-ray radiation, orcombinations thereof. In an exemplary method, the sheet, immediatelyafter coating, is passed through a gas-fired heating zone where solventsare evaporated and the resin is cured or dried. Preferably, the polymeris at least partially cured by heat. Heat curing is to raise thetemperature of the coating to accelerate cross-linking reaction. Heatcuring can be by various heating means such as an electric heating oven,hot air heating oven, infrared heating oven, and high-frequency heatingoven. For curing, a heating temperature and time are properly selectedin consideration of the formulation of a coating composition, the sizeand gage of sheet metal, the capacity of an oven, and other factors. Theparticular temperature is dependent on such things as the particularepoxy, curing agent and catalyst employed and curing time desired. Thetemperature, however, should not be so great that the cured coating isdegraded, for example, by decomposing. Generally, the drying or curingtreatment is carried out under normal pressure or reduced pressure at atemperature of at least about 50° C. to at most about 400° C. Preferablythe peak metal temperatures (PMT) for the coated metal sheets is atleast about 100° C., more preferably at least about 150° C. and mostpreferably at least about 200° C. Preferably the peak metal temperatures(PMT) for the coated metal sheets is at most about 350° C., morepreferably at most about 300° C. and most preferably at most about 275°C.

[0121] The time at the temperature of cure can be any practicable timeand is desirably as short as practical. Generally, the time at thecuring temperature is at least about 0.1 minute to at most about 24hours. Preferably the time at the cure temperature is at least about 10minutes, more preferably at least about 5 minutes and most preferably atleast about 0.5 minute. Preferably the time at the cure temperature isat most about 2 hours, more preferably at most about 1 hour and mostpreferably at most about 0.5 hour. As well within the knowledge of thoseskilled in the art, the temperature and time are in a relativerelationship and also the conditions vary depending on the properties ofcoating required.

[0122] Immediately after heating to cure or dry the coating, the coatedmetal sheet may then be subjected to quenching in order to harden thecoating prior to the final coiling of the sheet product. The quenchingcan be by any suitable means as known in the art such as by water orother coolant immersion, spray, or mist or by cold air. The coated metalsheet is then typically coiled by conventional means in metal coils.

[0123] The thickness of the coating of the present invention ispreferably in the range of from about 0.5 to about 30 microns.Preferably thickness of the coating is at least about 2 microns, morepreferably at least about 3 microns and most preferably at least about 4microns. Preferably the thickness of the coating is at most about 20microns, more preferably at most about 15 microns and most preferably atmost about 10 microns.

[0124] After curing, the applied coating composition, a metal sheethaving a cured resin coating adhered thereto is formed generally havingantimicrobial properties. Also, the coating that is formed, typically,has improved fingerprint resistance. The coating also protects thesurface from staining when tested against kitchen spills such asketchup, mustard and pickle juice.

[0125] Generally, a silver-bearing refractory compound is incorporatedinto a polyester or epoxy film coating to control the growth of harmfulbacteria, mold and mildew. These film coatings may be economicallyapplied to stainless or carbon steel products on full size productioncoils by means of roll coating. The antimicrobial properties may lastfor years depending on the intended application. Clear or pigmented filmcoatings can be used.

[0126] Preferably, silver ions are encapsulated within a zeoliterefractory. The zeolite powder is blended into either a polyester orepoxy resin. A thin film coating, about 0.00025″0 thick, is applied toeither a carbon or stainless steel sheet. The silver ions have greatmobility and can diffuse to the surface of the steel to inhibit thegrowth of bacteria and mold.

[0127] Silver has long been recognized for its safe antimicrobialproperties.

[0128] Coated products may be effective against many common food bornepathogens such as Escherichia coli, Salmonella and Listeriamonocytogenes as well as various types of mold including Aspergillusniger.

[0129] On metals, such as stainless steels, the zeolite refractorycompound, when added to a clear resin coating, hides fingerprints due tothe light scattering influence of the micron-scale diameter zeoliteparticles contained within the coating matrix. The resin coating alsoprotects the surface from staining when tested against kitchen spillssuch as ketchup, mustard and pickle juice.

EXAMPLE 1

[0130] Hot dipped galvanized steel (G-60, carbon steel having a zinccoating of about 0.6 oz. zinc/ft²) with a thickness of 0.045″ and awidth of 58.00″ is run though the roll coating process at a line speedof about 250 fpm. The steel strip is cleaned using an alkaline cleaner(PARCO CLEANER 1200) of potassium hydroxide at about 1 to about 2%concentration, dwell time of about 3 to about 10 seconds, and at atemperature of from about 150 to about 160° F. The steel strip is thenrinsed with a water rinse for about 2 to about 4 seconds at about 100°F.

[0131] The steel strip is then treated with a chemical conditioningrinse of PARCOLENE AT sodium phosphate compound with titanium, at about1 to about 1.5 lb per 100-gallon water, for a time from about 2 to about5 seconds, at a temperature of about 130 F.

[0132] The steel strip is then treated with a zinc phosphatepretreatment using Parker BONDERITE 1421 phosphoric acid based solutioncontaining nickel and fluoride additives, for a time about 5 to about 10seconds, with about 150 to about 250 mg/sq ft coating weight, at atemperature of about 140 to about 150 F. The strip is then rinsed with aclear water rinse for about 2 to about 4 seconds at about 100 F.

[0133] The steel strip is then treated with a chrome rinsepost-treatment of Parcolene 62 applied at a concentration of 2% inwater, composed of chromic acid, hydrofluoric acid and zinc chromate,for an exposure time of about 2 to about 5 seconds, at a pH of about 3.2to about 3.7, at a temperature of about 120 F.

[0134] By means of a roll coater, the strip is then coated with PPG's1HC5692 polyester melamine containing antimicrobial ZEOMIC powder(Sinanen Co., Inc., Japan). The liquid film coating is applied by meansof a conventional two roll coating system and utilizes one pick-up rollper side in contact with each applicator roll. The direction of theapplicator roll is opposed to the direction of the strip movement. Thisis referred to as reverse roll coating.

[0135] The metal sheet is cured in an oven to a Peak Metal Temperatureof about 440 F, producing a clear, polyester coating, with about 7 Wt-%silver zeolite, based on dried coating, with a coating thickness of fromabout 0.2 to about 0.3 mils, dry film thickness.

[0136] Adhesion as measured with 2T bend-test was excellent, as were theresults of Olsen dome tests. Subsequent efficacy tests conducted usingE. coli bacteria indicated more than a 3 log reduction in a 24 hourperiod relative to the initial inoculation levels.

EXAMPLE 2

[0137] Stainless steel strips, Type 304, at thicknesses of about 0.02″,0.030″, 0.036″, 0.048″, 0.060″, 0.075″, all with a width of about 50″,are run through the roll coating process at a line speed of about0.024″@300 fpm, 0.030″@300 fpm, 0.036″@325 fpm, 0.048″@275 fpm,0.060″@225 fpm, 0.075″@175 fpm.

[0138] The steel strip is cleaned using an alkaline cleaner (PARCOCLEANER 1200) of potassium hydroxide based, at about 1 to about 2%concentration, dwell time of about 3 to about 10 seconds, and at atemperature of from about 150 to about 160° F. The steel strip is thenrinsed with a water rinse for about 2 to about 4 seconds at about 100 F.

[0139] By means of a roll coater, the strip is then coated with PPG'sNupal 51OR Pretreatment, a water based phosphatized epoxy with propyleneglycol monomethyl ether. Nupal is applied from a solution at ambienttemperature, with a dwell time of about 1 second, and a coating weightof 10 mg/sq ft. The Nupal coating is then dried with warm air. Theantimicrobial coating used for stainless steel is PPG's 1HC5794 epoxymelamine containing antimicrobial ZEOMIC powder (Sinanen Co., Inc.,Japan).

[0140] After coating, the sheet passes through a gas fired heating zonewhere the solvents are evaporated and the resin is cured or dried to aPeak Metal Temperature (PMT) of about 460 F., water quenched to a metaltemperature of about less than 150 F., producing a clear, epoxy coating,with about 7 Wt-% silver zeolite, based on dried coating, with a coatingthickness of from about 0.2 to about 0.3 mils, dry film thickness.

[0141] Results indicated that the coating had excellent adhesion as seenby passing a 1T bend test. The coating hardness was measured as 5Hpencil. MEK rubs were found to be in the range of 5-10. Efficacy testresults were similar to those reported in Example 1.

EXAMPLE 3

[0142] Same as above with the following parameters:

[0143] Stainless steel strip, Type 304, at thickness of about 0.035″, awidth of about 37.50″, is coated at a line speed of about 275 fpm. Themetal is first cleaned with an alkaline cleaner at about 150° F. usingabout 40 to about 60 psi spray.

[0144] By means of a roll coater, the strip is then coated with PPG'sNupal 510 R Pretreatment, a water based phosphatized epoxy withpropylene glycol monomethyl ether. Nupal is applied from a solution atambient temperature, with a dwell time of about 1 second, and a coatingweight of 10 mg/sq ft. The Nupal coating is then dried with warm air.

[0145] After coating, the sheet passes through a gas fired heating zonewhere the solvents are evaporated and the resin is cured or dried to aPeak Metal Temperature of about 490 F., water quenched to a metaltemperature of less than about 150 F., producing a clear, epoxy coating,with about 7 Wt-% silver zeolite, based on dried coating, with a coatingthickness of from about 0.2 to about 0.3 mils, dry film thickness.

[0146] The coating has a hardness of 5H, MEK rubs of >120, and a bendtest of 1 T without coating loss. The higher PMT versus Example 2resulted in higher MEK rubs and a more complete cure. Efficacy resultswere similar to Example 1.

EXAMPLE 4

[0147] Same as above with the following parameters:

[0148] Hot dipped galvanized steel, G-60, with a thickness of 0.024″ anda width of 60.00″ is run through the roll coating process at a linespeed of about 300 fpm. The steel strip is cleaned using an alkalinecleaner at a temperature of about 150° F. using about 40 to about 60 psispray.

[0149] The steel strip is then treated with a chemical conditioningrinse of PARCOLENE No. 62, mat a temperature of about 120 F. The steelstrip is then treated with a zinc phosphate pretreatment using ParkerBONDERITE 1421 phosphoric acid based solution.

[0150] By means of a roll coater, the strip is then coated with ablue-pigmented epoxy containing antimicrobial ZEOMIC powder (SinanenCo., Inc., Japan). The liquid film coating is applied by means of aconventional two roll coating system and utilizes one pick-up roll perside in contact with each applicator roll.

[0151] The metal sheet is cured in an oven to a Peak Metal Temperatureof about 490 F., water quenched to a metal temperature of about lessthan about 150 F., producing a blue, epoxy coating, with about 7 wt-%silver zeolite, based on dried coating, with a coating thickness of fromabout 0.2 to about 0.3 mils, dry film thickness.

[0152] The coating hardness of 3H, MEK rubs of >75, and a bend test of 2T without coating loss indicated excellent physical properties wereobtained. Efficacy results were similar to those of Example 1.

EXAMPLE 5

[0153] Coating Characteristics: A thin, about 0.20 to about 0.30 mil,coating film may be readily applied by liquid roll coating. When a #4polished stainless steel surface is coated; the surface roughness isreduced from approximately 31 microinches in the transverse direction toapproximately 11 microinches. In the longitudinal direction, roughnessaverages increases from about 6 to about 11. The coating fills thegrooves within the polished surface decreasing roughness values in thetransverse direction and increasing roughness values in the longitudinaldirection of the steel. Thus, a more uniform surface roughness profileis maintained after liquid roll coating with the antimicrobial compoundadded to the epoxy resin coating. A #4 polished stainless steel is mostoften used in restaurant and in high-end kitchen appliances. A Type 304stainless steel is the most common grade for these applications.

Surface Roughness, Microinches, Average Values Type 304 Stainless Steel,Decorative Polished Finish

[0154] #4 Polished, Uncoated #4 Polished, Coated Ra, Transverse 31 11Ra, Longitudinal 6 11

[0155] Stainless polished steel finishes, when coated with theantimicrobial compound, tend to hide fingerprints and make the surfacehave a lower relative gloss finish compare to uncoated, standardpolished surfaces. Gloss measurements for representative stainless Type304 polished and polished and then coated surfaces are presented in thetable below. The angle of illumination is 20° from the normal to thesurface TABLE 1 #4 Polished, Uncoated #4 Polished, Coated Gloss,Transverse 39 28 Gloss, Longitudinal 74 40

[0156] Stainless polished finishes, when coated with the clear, epoxyresin that contains the antimicrobial compound tends to benondirectional with respect to surface roughness and gloss compared tothe conventional polished finishes. This coating yields a more uniformand blemish-free surface.

EXAMPLE 6

[0157] Efficacy testing was performed on both carbon and stainless steelproducts that had been coated with resins containing 7 wt% of theantimicrobial compound, AgION. These products were tested as followsagainst two of the most common food borne pathogens, E. coli andListeria. Results are and the testing protocols for this work arepresented below:

[0158] Organisms. Escherichia coli and Listeria monocytogenes

[0159] Preparation of test samples. Coupons (2″×2″) of stainless steel,both entirely bare and entirely AgION-coated, and galvanized steel,coated on one side only with AgION. Coupons were cleaned by swabbing,both sides, and all cut edges with 70% ethanol. Coupons were propped insterile empty petri dishes and allowed to air-dry.

[0160] Bacterial exposure to steel coupons. Petri dishes were closed andincubated at 37° C. All experiments were performed in duplicate.

[0161] Recovery of bacteria from steel coupons. After bacterialsuspensions had been in contact with steel coupons for 24 h, the couponswere inverted into the buffer solution in the bottom of the petri dish.Serial 10×dilutions in PBS were made of the buffer suspension, andplated as described above. TABLE 2 Effect on bacteria of 24-h exposureto AgION-coated surfaces.¹ Eseherichia coli Listeria monocytogenes Zero24 Hours Zero 24 Hours Sample Contact Contact Contact ContactIdentification Time Time Time Time Stainless 4.0 × 10⁵ 3.0 × 10⁶ 1.5 ×10⁴ 1.0 × 10⁷ Stainless + 4.0 × 10⁵ <1 1.5 × 10⁴ <1 AgION Galvanized 4.0× 10⁵ 3.4 × 10⁶ 1.5 × 10⁴ 1.5 × 10⁷ Galvanized + 4.0 × 10⁵ <1 1.5 × 10⁴<1 AgION

[0162] As shown from the test data, almost all of the bacteria presentof the surfaces of treated steel samples are eliminated after the 24 hrstime period. Control steel surfaces exhibited an increase in bacterialcounts occurred during the test.

1. A process of manufacturing a metal sheet precoated with anantimicrobial polymer coating, comprising: providing a metal sheetsubstrate having two opposed planar surfaces comprising a base metalselected from the group consisting of aluminum, iron, nickel, titanium,molybdenum, magnesium, manganese, copper, silver, lead, tin, chromium,beryllium, tungsten, cobalt and alloys thereof; cleaning the surface ofthe substrate wherein cleaning comprises removing bulk and molecularorganic contaminants; pretreating at least one planar surface of thesubstrate to promote adhesion of a polymer coating; applying a polymercoating onto at least one planar surface of the substrate by rollcoating the substrate with a polymer containing an anti-microbial powdercomprising core particles associated with an antimicrobial metalcomponent; wherein the content of the antibiotic powder is in the rangeof from about 0.2 to about 30 weight percent of the polymeric coating;wherein the core particle is an oxide selected from the group consistingof titanium, aluminum, zinc and copper, sulfates of calcium, strontiumand barium, zinc sulfide, copper sulfide, zeolites, zirconium phosphate,mica, talc, kaolin, mullite, silica and mixtures thereof; wherein theantimicrobial metal component is selected from the group consisting ofsilver, copper, zinc, mercury, tin, lead, bismuth, cadmium, chromium,cobalt, nickel, and thallium ions and mixtures thereof; and treating thecoated substrate to produce at least a partially hardened and adheredantimicrobial coating on the final sheet product.
 2. The process ofclaim 1 wherein the base metal is a metal selected from the groupconsisting of steel, zinc, iron, aluminum, copper and mixtures thereof.3. The process of claim 2 wherein the metal sheet is provided as acontinuous strip.
 4. The process of claim 3 wherein the base metal is anickel alloy selected from the group consisting of steel, zinc, zincbased alloys, zinc coated steel, zinc aluminum alloy coated steel,aluminum and aluminum alloy.
 5. The process of claim 3 wherein the basemetal is a nickel alloy selected from the group consisting of nickelmanganese, nickel-aluminum, nickel silver, nickel bronze andnickel-silicon.
 6. The process of claim 3 wherein the base metal is acopper alloy such as brass, bronze, silicon bronze, silicon brass,nickel silver and nickel bronze
 7. The process of claim 3 wherein thebase metal is an aluminum-based metal selected from the group consistingof pure aluminum, aluminum oxide, and aluminum alloy.
 8. The process ofclaim 7 wherein the base metal is an aluminum alloy selected from thegroup consisting of Al—Cl, Al—Mg, Al—Si, Al—Cu—Ni—Mg and Al—Si—Cu—Ni—Mg.9. The process of claim 3 wherein the base metal is an iron-based metalselected from the group consisting of pure iron, iron oxide, carbonsteel, Ni steel, Cr steel, Ni—Cr steel, Cr—Mo steel, Ni—Cr—Mo steel,stainless steel, silicon steel, Permalloy, non-magnetic steel, magneticsteel, and cast steel.
 10. The process of claim 3 wherein the base metalis an alloy steel selected from the group consisting of carbon steel, Nisteel, Cr steel, Ni—Cr steel, Cr—Mo steel, stainless steel, siliconsteel and Permalloy.
 11. The process of claim 3 wherein the base metalis galvanized steel.
 12. The process of claim 3 wherein the cleaningstep comprises a cleaning method selected from the group consisting ofsolvent cleaning, emulsion cleaning, alkaline cleaning, acid cleaning,pickling, salt bath descaling ultrasonic cleaning, and combinationsthereof.
 13. The process of claim 12 wherein the cleaning step is byalkaline cleaning with an alkaline solution comprising one or moreagents selected from the group consisting of caustic soda, soda ash,alkaline silicates, sodium hydroxide, sodium carbonate, sodiummetasilicate, phosphates, alkaline builders, ammonium acid phosphate,ammonium hydroxide, monoethanol amine, and dimethylamine oxide.
 14. Theprocess of claim 13 wherein the alkaline solution additionally containsone or more of the agents selected from the group consisting ofcomplexing agents, surfactants, sequestrant, builders, surface-activeagents, defoaming agents, and mixtures thereof.
 15. The process of claim14 wherein the alkaline builder comprises one or more of the agentsselected from the group consisting of sodium silicate, trisodiumphosphate, caustic soda, disodium phosphate, sodium pyrophosphate,sodium carbonate, sodium bicarbonate, sodium tripolyphosphate, andsodium sesquicarbonate.
 16. The process of claim 13 wherein thetemperature of the alkaline solution is between about 25° and about 95°C.
 17. The process of claim 12 wherein the metal surface having beencontacted by the cleaning solution is rinsed with water.
 18. The processof claim 17 wherein the rinsing is followed by drying.
 19. The processof claim 13 wherein the pretreating creates a chemical conversioninterlayer coating selected from the group consisting of a silane,phosphate, chromate, epoxy, oxide, adhesive and mixtures thereof. 20.The process of claim 19 wherein the interlayer is formed by contactingthe metal with a composition selected from the group consisting ofchromium phosphate, chromium chromate, zinc phosphate, iron phosphate,or an epoxy.
 21. The process of claim 20 wherein the interlayer isformed by contacting the metal with an aqueous phosphating compositioncomprising phosphoric acid and a divalent metal ion wherein thecomposition has total phosphate content from about 0.01 to about 3moles/liter and the metal ion is selected from the group consisting ofdivalent transition metal ions and alkaline earth divalent metal ions.22. The process of claim 21 wherein the divalent metal ion is selectedfrom the group consisting of Mn, Co, Fe, Ni, and Zn.
 23. The process ofclaim 21 wherein the divalent metal ion is selected from the groupconsisting of Mg, Ca, Sr, and Ba.
 24. The process of claim 21 whereinthe divalent metal ion is selected from the group consisting of Fe, Niand Zn.
 25. The process of claim 24 wherein the phosphating compositionadditionally comprises an oxidant is selected from the group consistingof bromate, chlorate, nitrate, nitrite, organic nitro compounds,perborate, persulfate or hydrogen peroxide, m-nitrobenzene sulfonate,nitrophenol and combinations thereof.
 26. The process of claim 24wherein the phosphating composition additionally comprises one or morecompounds selected from the group consisting of sulfate, fluoride,silicofluoride, boron fluoride, citrate, tartrate, hydroxy-carboxylicacids, aminocarboxylic acids, condensed phosphates, silicates, alkalimetal metasilicate, alkali metal orthosilicate, and alkali metaldisilicate.
 27. The process of claim 24 wherein the phosphatingcomposition additionally comprises silicate.
 28. The process of claim 21wherein the metal substrate is predominantly aluminum and wherein thephosphating composition includes an activator present as fluoride ionsin amounts up to 1.0 moles/liter.
 29. The process of claim 21 whereinthe metal substrate is predominantly galvanized steel or steel andwherein the phosphating composition includes boric acid in an amount ofat least 0.02.
 30. The process of claim 24 wherein the interlayer isbetween about 0.01 to about 30 microns thick.
 31. The process of claim24 wherein the interlayer is at least partially dried by heating. 32.The process of claim 31 wherein the drying temperature is between about25° and about 95° C.
 33. The process of claim 31 wherein the dryingtemperature is from at least 50° C.
 34. The process of claim 13 whereinthe polymer is an organic polymer material selected from the groupconsisting of acetate rayon, acrylic resins,acrylonitrile-butadiene-styrene resins and acrylic resins, aliphatic andaromatic polyamides, aliphatic and aromatic polyesters, allyl resins,butadiene resins, chlorinated polyethylene, conductive resins,copolymerised polyamides, copolymers of ethylene and vinyl acetate,cuprammonium rayons and natural and synthetic rubbers, EEA resins, epoxyresins, ether ketone resins, ethylene vinyl alcohol, fluorine resins,fluorocarbon polymers, fluoroplastics, high density polyethyelenes,ionomer resins, liquid crystal polymer, low density polyethylenes,melamine formaldehyde, natural polymers such as cellulosics, nylons,phenol-formaldehyde plastic, phenolic resins, polyacetal, polyacrylates,polyacrylonitrile, polyamide, polyamide-imide, polyaryletherketone,polybutadiene, polybutylene terephthalate, polybutylene, polycarbonate,polycarbonates, polydicyclopentadiene, polyketones, polyester blockcopolymers, polyesters, polyesterurethane, polyesterurethaneurea,polyether and polyester block polymers, polyether ketoneketonepolyetherether ketone polyetherimide, polyethers, polyethersulfone,polyetherurethane, polyetherurethaneurea, polyethylene isophthalate,polyethylene terephthalate, polyethylene, polyethylenechlorinates,polyglycolic acid, polyhexamethylene terephthalate, polyimide,polylactic acid, polymethylpentene, poly-m-phenylene isophthalamide,polyolefins, polyphenylene oxide, polyphenylene sulfide,polyphthalamide, poly-p-phenylene terephthalamide, polypropylene,polysiloxanes, polystyrene, polysulfides, polysulfone,polytetrafluoroethylene, polyurethane, polyvinyl acetate, polyvinylalcohols, polyvinylchloride, polyvinylidene chloride, polyvinylidenefluoride and polyvinyl fluoride, rayon, reconstituted silk andpolysaccharides, reinforced polyethylene terephthalate resins, segmentedpolyurethane elastomers, silicone resins, elastane elastomers,styrene-type specific resins, thermoplastic polyurethane elastomers,phenol-formaldehyde copolymer, triacetate rayon, unsaturated polyesterresins, urea resins, urethane resins, vinyl chloride resins, vinylpolymers, vinylidene chloride resins and copolymers, terpolymers andmixtures thereof.
 35. The process of claim 20 wherein the polymer isselected from the group consisting of acrylic resins, polyester resins,polyethylene, polypropylene, epoxy resins, polyurethane resins, olefinresins, polyamide resins, ethylene-vinyl acetate copolymer,ethylene-vinyl alcohol copolymer, polyvinyl chloride, polyvinylidenechloride, polystyrene, ABS resin, polyethylene terephthalate, nylon,polycarbonate and copolymers, terpolymers and mixtures thereof.
 36. Theprocess of claim 20 wherein the polymer is selected from the groupconsisting of aminoalkyd resins, aminoacrylic resins, polyvinyl chlorideand polyesters.
 37. The process of claim 20 wherein the polymer is apolyester.
 38. The process of claim 20 wherein the polymer is an epoxyselected from the group consisting of phenolic-modified epoxies,polyester-modified epoxies, epoxy-modified polyvinyl chloride, and crosslinkable epoxies.
 39. The process of claim 20 wherein the polymer is anepoxy.
 40. The process of claim 35 wherein the core particle is anatural zeolite selected from the group consisting of analcime,chabazite, clinoptilolite, erionite, faujasite, mordenite, andphillipsite.
 41. The process of claim 35 wherein the core particle is asynthetic zeolite selected from the group consisting of A-type zeolite,X-type zeolite, Y-type zeolite, and mordenite.
 42. The process of claim41 wherein the core particle is a synthetic zeolite whoseion-exchangeable ions are partially or completely ion-exchanged withantibiotic metal ions.
 43. The process of claim 42 wherein theion-exchangeable ions are selected from the group consisting of sodiumions, potassium ions, calcium ions, magnesium ions and iron ions andwherein the antibacterial metals ions are selected from the groupconsisting of silver, copper, zinc, mercury, tin, lead, bismuth,cadmium, chromium, cobalt, nickel, and thallium ions or mixturesthereof, and wherein the zeolite particles retain the antibacterialmetal ions at ionic exchange sites of the zeolite in an amount less thanthe ion exchange saturation capacity of the zeolite.
 44. The process ofclaim 43 wherein the zeolite is ion-exchanged with metal ions in anamount less than about 90% of the ion-exchangeable saturation capacityof the zeolite particles.
 45. The process of claim 44 wherein theantibacterial metals ions are selected from the group consisting ofsilver, copper or zinc ions or mixtures thereof.
 46. The process ofclaim 44 wherein the antibacterial metal ions are silver.
 47. Theprocess of claim 45 wherein additional metal ions selected from thegroup consisting of sodium, potassium, magnesium, calcium, aluminum,titanium, cerium and ammonium ion co-exist on the zeolite.
 48. Theprocess of claim 44 wherein the amount of antimicrobial component on thecore particle is at least about 0.1% by weight, based on anhydrouszeolite plus metal.
 49. The process of claim 44 wherein the amount ofantimicrobial component on the core particle is at least about 0.2% byweight, based on anhydrous zeolite plus metal.
 50. The process of claim44 wherein the amount of antimicrobial component on the core particle isat most about 20% by weight, based on anhydrous zeolite plus metal. 51.The process of claim 44 wherein the amount of antimicrobial component onthe core particle is at most about 15% by weight, based on anhydrouszeolite plus metal.
 52. The process of claim 44 wherein the amount ofantimicrobial component on the core particle is at most about 10% byweight, based on anhydrous zeolite plus metal.
 53. The process of claim44 wherein the anti-microbial powder has a second coating of acomposition selected from the group consisting of silica, silicates,silicon dioxide, borosilicates, aluminosilicates, alumina, aluminumphosphate, zinc, zinc oxide, zinc silicate, copper, copper oxide, andmixtures thereof.
 54. The process of claim 53 wherein the second coatingcomprises from about 0.1 to about 20% by weight, based on anhydrouszeolite plus metal.
 55. The process of claim 44 wherein theantimicrobial powder is additionally coated with a dispersion enhancingcoating selected from the group consisting of resin, hydrous metaloxide, and mixtures thereof.
 56. The process of claim 44 wherein theantimicrobial powder has an average particle size less than about 10microns.
 57. The process of claim 44 wherein the antimicrobial powderhas an average particle size less than about 6 microns.
 58. The processof claim 44 wherein the antimicrobial powder has an average particlesize greater than about 0.1 microns.
 59. The process of claim 44 whereinthe antimicrobial powder has an average particle size greater than about0.2 microns.
 60. The process of claim 44 wherein the polymer furthercomprises at least one additional component selected from the groupconsisting of defoamers, polymerization catalysts, stabilizers,delustering agents, whitening agents, pigments, fillers, plasticisers,ultraviolet absorbers, antioxidants, light stabilizers, ultravioletstabilizers, processing stabilizers, and metal deactivators.
 61. Theprocess of claim 44 wherein the roll coater is a two-roll coater
 62. Theprocess of claim 44 wherein the polymer is applied by two or morecoaters placed in series.
 63. The process of claim 61 wherein theantimicrobial polymer coating is applied onto both opposed planarsurfaces of the sheet metal.
 64. The process of claim 61 wherein thepolymer coating is at least partially hardened by a method selected fromthe group consisting of heat, infrared radiation, fluorescent radiation,ultraviolet radiation, gamma or beta radiation, X-ray radiation, orcombinations thereof.
 65. The process of claim 64 wherein cleaningcomprises deoxidizing the surface by immersion in an acid solution, andrinsing in water.
 66. The process of claim 61 wherein the metal sheet ismade of a base metal material selected from the group consisting ofaluminum, aluminum alloys, magnesium, and magnesium alloys.
 67. Theprocess of claim 61 wherein the metal sheet is stainless steel andwherein the coating has a thickness of from about 1 to about 30 microns.68. The process of claim 61 wherein the coating after forming-processedis heated at a temperature of 100° to 300° C.
 69. A metal sheetprecoated with an antimicrobial polymer coating manufactured by themethod of claim 1, 10, 20, 35 or
 42. 70. A method of increasing stainresistance of a metal sheet by the method of claim 1, 10, 20, 35 or 42.71. A method of increasing fingerprint resistance of a metal sheet bythe method of claim 1, 10, 20, 35 or 42.